1. Field of the Invention
The present invention relates to an alarm device for vehicle which calls a driver's attention to a danger of contacting or colliding with an obstacle at a time of changing lanes for avoiding the danger.
2. Discussion of Background
A conventional alarm device operable at a time of changing lanes is disclosed in, for example, JP-A-10-166971. This discloses that an approach of an object positioned in a side back of a vehicle is detected; a lane change and so on are judged in case that a turn signal indicator switch is not operated; and a driver is alerted.
FIG. 20 schematically illustrates a structure of the conventional alarm device.
In FIG. 20, numerical 1 designates a scan laser radar for detecting the object; numerical reference 2 designates a velocity sensor for detecting a velocity of the vehicle; numerical reference 3 designates a controller for controlling an alarm upon inputs from the scan laser radar 1 and the velocity sensor 2; numerical reference 4 designates a primary alarm lamp controlled by the controller 3; numerical reference 5 designates a secondary alarm lamp controlled by the controller 3; and numerical reference 6 designates an alarm buzzer controlled by the controller 3.
FIG. 21 is a flow chart of processes conducted by the conventional alarm device.
An operation thereof will be described in reference of the flow chart of FIG. 21.
In an alarm controlling routine for controlling the alarm by the controller 3, an area subjected to the alarm is set in Step J1. In Step J2, it is judged whether or not a representative of an object to be detected exists within area subjected to the alarm, in other words, whether or not a succeeding vehicle enters the area. When it is recognized that the succeeding vehicle exists, it is judged whether or not a relative velocity is a predetermined value or more in Step J3, wherein when the relative velocity is the predetermined value or more, the primary alarm lamp 4 is lit in Step J4 to awaken primary attention to the driver. In case that the succeeding vehicle goes out of the area subjected to the alarm in Step J2 or that the relative velocity is smaller than the predetermined value in Step J3, it is regarded that a degree of danger to a driver's own vehicle is low, wherein Step J7 is processed to turn off the primary alarm lamp 4, the secondary alarm lamp 5, and the alarm buzzer 6, each under operation. When the primary alarm lamp 4 is lit, it is judged whether or not a displacement amount of the representative in its width directions is larger than a predetermined value, wherein when the displacement amount is larger than the predetermined value, it is judged that a lane is changed and the secondary alarm lamp 5 and the alarm buzzer 6 are actuated in Step J6. When the displacement amount is smaller than the predetermined value, the secondary alarm lamp 5 and the alarm buzzer 6 are turned off in Step J7.
According thereto, in case that an object such as a succeeding vehicle approaches from a back of a driver's own vehicle when the own vehicle changes lanes or turns right or left without manipulating a turn signal indicator switch, it is possible to certainly alert, whereby a capability of avoiding accidents is improved even in cases such that a driver is careless.
However, according to the method of judging a lane-change based on the displacement amount of the object to be detected in its width directions as the above conventional technique, the judgement is conducted only after the own vehicle starts to change lanes. Therefore, there is a time lag in the judgement and a danger of contacting with a succeeding vehicle is left. To deal therewith, it is considered to judge whether or not an alarm is actuated regardless of a manipulation of a turn signal indicator switch. However, in case that the own vehicle runs through a lane adjacent to the opposite side of the road or lanes adjacent to where the own vehicle runs are congested, objects to be detected exist within an area subjected to alarm, whereby alarms are frequently actuated depending on relative velocities, to resultantly make a driver feel uncomfortable.